The invention relates to a silo (a silo combination) for mixing stored material.
Homogenizing silos have been known where turning over and the intermixing of material are achieved by intensive aeration of bottom sections. The advantage lies in achieving a high homogenization of the material. The disadvantage of this system lies in the size of the silos which is required. Conditional on this large silo unit, large quantities of air at a high pressure (expenditure of power) are required in order to make the material turn over and thus intermix it. A further disadvantage of this system lies in the discontinuity of the mixing process, since a charge always has to be mixed over an extended period of time of several hours.
Continuous mixing silos are also known, in which different layers are cut up and mixed up by gravitation at the outlet by the formation of "cones" or "funnels" of layered material which extend down toward an outlet. The advantages lie in the low power requirement and in the continuity of the mixing process. The disadvantage of this system lies in the limited mixing performance.
The invention is directed to a silo of the initially mentioned type which makes it possible to combine the advantages of both types of silos (homogenizing silo and continuous mixing silo) with simultaneous elimination of the disadvantages.
According to the invention, this is accomplished by the combination of a mixing silo with a homogenizing silo, whereby the layers of material stored in the mixing silo will flow into one another and be mixed in consequence of the formation of cones when material is transferred from the mixing silo to the homogenizing silo via dosing and blocking organs, and whereby the quantity of material drawn from the mixing silo into the homogenizing silo is homogenized with the help of aerating elements.
At the same time, residual homogenization according to the invention takes place in the outlet connected homogenizing silo. The advantage of this silo according to the invention consists in the fact that it is possible to combine the known types of silo without causing new disadvantages thereby.
Premixing of the material is accomplished by emptying the mixing silo into the homogenizing silo in such a way that the layers of material present in the mixing silo flow into one another and are mixed by the formation of so-called cones. Perfect operation of the silo is achieved only when the flow of the bulk material in the mixing silo is correct. That portion of the mixing silo having bulk material movement should be as large as possible during emptying, i.e., the bulk material should be drawn off as evenly as possible over the entire inside space of the silo. The drawing off from the mixing silo into the homogenizing silo takes place in a controlled manner by way of "dosing and locking organs" or flow control gates, and so-called cones develop in the mixing silo above the pertinent drawing off element; that is to say, the various layers of material located above the locking organ are funneled in the direction of the drawing off aperture. One dosing and locking organ after another is triggered at predetermined time intervals and, simultaneously, the required aeration for the associated bottom section takes place. Every such emptying section of the mixing silo is triggered successively, or else according to a predetermined sequence, in such a way that the material in the mixing silo will remain approximately level during the emptying process. Accordingly, during the emptying process from the mixing silo into the following homogenizing silo, an intermixing of the layers of material located in the silo takes place. The quantity of material drawn off into the homogenizing silo from the mixing silo, however, will still have heterogeneities. In prior art silos in which the formation of cones is not controlled, as for example by successively activating different drawing-off apertures, it is possible that bulk materials freshly put into the mixing silo might punch or seep through to the outlet aperture without participating in the mixing process. In contrast thereto, in the case of the silo of the invention, and because of the formation of cones, the composition of the material drawn from the mixing silo into the homogenizing silo corresponds to the composition of the quantity of material stored in the silo. This means that the material drawn into the homogenizing silo constitutes a representative cross section of the entire quantity of bulk material which had been stored in the silo of the invention. The further homogenization of this quantity of material in the homogenizing silo therefore produces a homogenized mass having the composition of the quantity of bulk material stored into the silo of the invention. However, because of the optimal utilization of the mixing silo and of the homogenizing silo, a very high effect of intermixing will be achieved. The silo of the invention operates in a continuous mixing process, so that only as much material is drawn from the mixing silo into the homogenizing silo as is removed from the homogenizing silo.
The completely homogenous mixing of the bulk material stored in the silo of the invention is brought about by the above-described combination of the mixing silo with the homogenizing silo.
According to a particularly preferred embodiment of the silo of the invention, the mixing silo is fed by way of a distributor "spider" which produces a spider-like distribution, making it possible to feed material of variable quality in layers into the silo of the invention.
According to a further especially preferred embodiment, the air blow in by way of aeration elements in the bottom of the homogenizing silo is taken out via a filter on the ceiling of the homogenizing silo.
In order to allow material in the homogenizing silo to be turned over, an expansion chamber will have to be provided above the material to be mixed. The mixing process is brought about by the fact that, in a so-called, active aeration zone of the bottom, a considerable larger quantity of air is blown in than in the inactive zone, with the consequence that above this bottom section of the active zone, the material will rise upward and flow over to the less aerated areas, which on their part will feed the active zone with material as a result of low (weak) aeration.
Any impeding of this turn-over process as a result of a non-secured expansion space at the top of the homogenizing silo would exclude any turning over and thus any intermixing of the material.
The free (empty) upper space in the homogenizing silo is secured by supplying material from the mixing silo into the homogenizing silo regulated via dosing slides. The control of these dosing slides can be accomplished by a level recorder in the homogenizing silo.